Fix up timestamp quoting issue.

src/Db/Adapter/AbstractAdapter.php

@@ -1040,10 +1040,22 @@ public function castToBool($value): mixed
      */
     protected function getDefaultValueDefinition(mixed $default, ?string $columnType = null): string
     {
+        $datetimeTypes = [
+            static::PHINX_TYPE_DATETIME,
+            static::PHINX_TYPE_TIMESTAMP,
+            static::PHINX_TYPE_TIME,
+            static::PHINX_TYPE_DATE,
+        ];
+
         if ($default instanceof Literal) {
             $default = (string)$default;
-        } elseif (is_string($default) && stripos($default, 'CURRENT_TIMESTAMP') !== 0) {
-            // Ensure a defaults of CURRENT_TIMESTAMP(3) is not quoted.
+        } elseif (is_string($default) && stripos($default, 'CURRENT_TIMESTAMP') === 0) {
+            // Only skip quoting CURRENT_TIMESTAMP for datetime-related column types.
+            // For other types (like string), it should be quoted as a literal string value.
+            if (!in_array($columnType, $datetimeTypes, true)) {
+                $default = $this->quoteString($default);
+            }
+        } elseif (is_string($default)) {
             $default = $this->quoteString($default);
         } elseif (is_bool($default)) {
             $default = $this->castToBool($default);

src/Db/Adapter/MysqlAdapter.php

@@ -624,7 +624,8 @@ static function ($value) {
                 $extra = ' ' . implode(' ', $extras);
 
                 if (($row['Default'] !== null)) {
-                    $extra .= $this->getDefaultValueDefinition($row['Default']);
+                    $phinxTypeInfo = $this->getPhinxType($row['Type']);
+                    $extra .= $this->getDefaultValueDefinition($row['Default'], $phinxTypeInfo['name']);
                 }
                 $definition = $row['Type'] . ' ' . $null . $extra . $comment;
 

tests/TestCase/Db/Adapter/AbstractAdapterTest.php

@@ -4,6 +4,7 @@
 namespace Migrations\Test\Db\Adapter;
 
 use Migrations\Db\Adapter\AbstractAdapter;
+use Migrations\Db\Literal;
 use Migrations\Test\TestCase\Db\Adapter\DefaultAdapterTrait;
 use PDOException;
 use Phinx\Config\Config;
@@ -144,4 +145,132 @@ public function fetchAll(string $sql): array
 
         $this->assertEquals([], $adapter->getVersionLog());
     }
+
+    /**
+     * Test CURRENT_TIMESTAMP default value quoting behavior (bug #1891).
+     *
+     * This test verifies that CURRENT_TIMESTAMP is only treated as a SQL function
+     * for datetime-related column types. For other column types like string,
+     * 'CURRENT_TIMESTAMP' should be quoted as a literal string value.
+     *
+     * @see https://github.com/cakephp/phinx/issues/1891
+     */
+    #[DataProvider('currentTimestampDefaultValueProvider')]
+    public function testCurrentTimestampDefaultValueQuoting($default, $columnType, $expected)
+    {
+        $adapter = new class (['version_order' => Config::VERSION_ORDER_CREATION_TIME]) extends AbstractAdapter {
+            use DefaultAdapterTrait;
+
+            public function quoteString(string $value): string
+            {
+                return "'" . $value . "'";
+            }
+
+            // Expose the protected method for testing
+            public function testGetDefaultValueDefinition(mixed $default, ?string $columnType = null): string
+            {
+                return $this->getDefaultValueDefinition($default, $columnType);
+            }
+        };
+
+        $actual = $adapter->testGetDefaultValueDefinition($default, $columnType);
+        $this->assertEquals($expected, $actual);
+    }
+
+    /**
+     * Data provider for CURRENT_TIMESTAMP quoting test.
+     *
+     * @return array
+     */
+    public static function currentTimestampDefaultValueProvider(): array
+    {
+        return [
+            // CURRENT_TIMESTAMP on datetime types should NOT be quoted
+            'CURRENT_TIMESTAMP on datetime' => [
+                'CURRENT_TIMESTAMP',
+                AbstractAdapter::PHINX_TYPE_DATETIME,
+                ' DEFAULT CURRENT_TIMESTAMP',
+            ],
+            'CURRENT_TIMESTAMP on timestamp' => [
+                'CURRENT_TIMESTAMP',
+                AbstractAdapter::PHINX_TYPE_TIMESTAMP,
+                ' DEFAULT CURRENT_TIMESTAMP',
+            ],
+            'CURRENT_TIMESTAMP on time' => [
+                'CURRENT_TIMESTAMP',
+                AbstractAdapter::PHINX_TYPE_TIME,
+                ' DEFAULT CURRENT_TIMESTAMP',
+            ],
+            'CURRENT_TIMESTAMP on date' => [
+                'CURRENT_TIMESTAMP',
+                AbstractAdapter::PHINX_TYPE_DATE,
+                ' DEFAULT CURRENT_TIMESTAMP',
+            ],
+            'CURRENT_TIMESTAMP(3) on datetime' => [
+                'CURRENT_TIMESTAMP(3)',
+                AbstractAdapter::PHINX_TYPE_DATETIME,
+                ' DEFAULT CURRENT_TIMESTAMP(3)',
+            ],
+
+            // CURRENT_TIMESTAMP on non-datetime types SHOULD be quoted (bug #1891)
+            'CURRENT_TIMESTAMP on string should be quoted' => [
+                'CURRENT_TIMESTAMP',
+                AbstractAdapter::PHINX_TYPE_STRING,
+                " DEFAULT 'CURRENT_TIMESTAMP'",
+            ],
+            'CURRENT_TIMESTAMP on text should be quoted' => [
+                'CURRENT_TIMESTAMP',
+                AbstractAdapter::PHINX_TYPE_TEXT,
+                " DEFAULT 'CURRENT_TIMESTAMP'",
+            ],
+            'CURRENT_TIMESTAMP on char should be quoted' => [
+                'CURRENT_TIMESTAMP',
+                AbstractAdapter::PHINX_TYPE_CHAR,
+                " DEFAULT 'CURRENT_TIMESTAMP'",
+            ],
+            'CURRENT_TIMESTAMP on integer should be quoted' => [
+                'CURRENT_TIMESTAMP',
+                AbstractAdapter::PHINX_TYPE_INTEGER,
+                " DEFAULT 'CURRENT_TIMESTAMP'",
+            ],
+
+            // Regular string defaults should always be quoted
+            'Regular string default' => [
+                'default_value',
+                AbstractAdapter::PHINX_TYPE_STRING,
+                " DEFAULT 'default_value'",
+            ],
+            'Regular string on datetime' => [
+                'some_string',
+                AbstractAdapter::PHINX_TYPE_DATETIME,
+                " DEFAULT 'some_string'",
+            ],
+
+            // Literal values should not be quoted
+            'Literal value' => [
+                Literal::from('NOW()'),
+                AbstractAdapter::PHINX_TYPE_DATETIME,
+                ' DEFAULT NOW()',
+            ],
+
+            // Boolean defaults
+            'Boolean true' => [
+                true,
+                AbstractAdapter::PHINX_TYPE_BOOLEAN,
+                ' DEFAULT 1',
+            ],
+            'Boolean false' => [
+                false,
+                AbstractAdapter::PHINX_TYPE_BOOLEAN,
+                ' DEFAULT 0',
+            ],
+
+            // Null columnType (should quote CURRENT_TIMESTAMP when type is unknown)
+            'CURRENT_TIMESTAMP with null column type' => [
+                'CURRENT_TIMESTAMP',
+                null,
+                " DEFAULT 'CURRENT_TIMESTAMP'",
+            ],
+        ];
+    }
 }